The present invention relates to a coupler for attaching, removing, or replacing an attachment such as a bucket, a clamshell bucket, or a vibration crusher which is secured to the end of an arm of a working machine such as a power shovel.
A working machine (e.g. power shovel) widely used for engineering work must be provided with various attachments such as a clamshell bucket or a vibration crusher instead of a bucket depending on the type of work.
In a small-scale construction site, it is generally necessary to carry out various types of work utilizing one power shovel. In such construction work, the attachment must be replaced each time the type of work changes.
An attachment coupler has been used in order to easily and quickly perform the replacement operation.
For example, a conventional coupler shown in FIG. 10 includes a base 120A and a slider 130A, and is attached to a power shovel by pivotally attaching the base portion of the coupler to a front link 82 and an arm 81 using pins 121 and 131.
A conventional coupler shown in FIG. 11 includes a link plate 120B and a link plate 130B, and is attached to a power shovel by pivotally attaching the base portion of the coupler to the front link 82 and the arm 81 using the pins 121 and 131.
U-shaped portions 122 and 132 which face each other (FIG. 10) or face in opposite directions (FIG. 11) are provided on the end of the coupler, and an expansion-contraction tool 140 such as a screw rod or a hydraulic cylinder is provided for adjusting the distance between the U-shaped portions 122 and 132.
Pins 2 and 3 are provided in advance to an attachment 1 such as a bucket. The pins 2 and 3 of the bucket are inserted into the U-shaped portions 122 and 132. The bucket 1 is secured by applying a pulling force (FIG. 10) or a separating force (FIG. 11) using the expansion-contraction tool 140.
In the coupler having such a structure, an abnormal force may be applied to the pins or the U-shaped portions 122 and 132 when foreign matter enters the U-shaped portions 122 and 132, whereby the coupler may break or the pins 2 and 3 of the attachment 1 may be removed from the U-shaped portions 122 and 132. In the worst case, the attachment 1 falls, thereby endangering the workers.
U.S. Pat. No. 4,067,467 discloses technology of securing an attachment by engaging posts provided on the ends of an arm and a front link with sockets provided in a bucket. However, since a dedicated engagement structure must be provided to the coupler and the attachment, this technology lacks versatility and results in poor workability.